A screen grab taken from a handout video obtained from the Egyptian Defense Ministry shows search operations for a missing EgyptAir flight off the Egyptian coast, north of Alexandria, Egypt, on May 20.

Rescuers have gathered human remains, luggage, and seats from the wreckage of EgyptAir Flight 804 in the waters off Egypt, as news reports said smoke may have been detected in a lavatory before the jet crashed.

Search crews were combing the waters about 300 kilometers north of Alexandria looking for the black-box flight recorders that they hope will shed more light on why the plane went down suddenly on May 19.

Officials said the Airbus A320 on its way from Paris was cruising normally in clear night skies on its way to Cairo when it lurched left, then right, spun all the way around and plummeted 12,000 meters into the sea.

No distress signal was issued. All 66 people on board died.

Relatives of the victims of the missing EgyptAir flight MS804 hold an absentee funeral prayer in a mosque nearby Cairo airport, in Cairo on May 20.

​Meanwhile, CNN, The Wall Street Journal, and an aviation industry publication reported that smoke may have been detected on board the craft before it went down.

The Aviation Herald, a website that covers the civil aviation industry, said information transmitted through the plane's Aircraft Communications Addressing and Reporting System showed that smoke was detected in the lavatory near the cockpit.

The messaging system transmits data from the plane to the ground in the form of a series of messages.

Investigators at Charles de Gaulle Airport in Paris, where the plane took off, scrutinized the passenger list and questioned ground-crew members.

Egyptian Prime Minister Sherif Ismail said it was too early to rule out any cause. The aviation minister said a terrorist attack was more likely than a technical failure, but offered no evidence.

No militant group has claimed responsibility for bringing down the jet, which has so far helped keep officials from labeling the incident as a terrorist act.

By comparison, a group linked to Islamic State radicals claimed responsibility for the downing of a Russian jet over the Sinai Peninsula within hours of the crash in October.

That crash, which killed 224 people, devastated Egypt's tourist industry, a primary source of badly needed foreign exchange for the country of 80 million people. Another similar attack would further crush hopes of the tourism industry recovering.